My Admin account was initially set up with the same email address as my regular AD account. When I attempted to login with my AD account, this combination of settings caused the Admin account to be inaccessible. I had to change the Admin account password (and email address for safety) using a different account with administrator role to fix the issue.

Users cannot update their profile when Prevent Email Change is enabled. The validation on WordPress’ save changes alerts that the user must enter their email address to continue, even though the field has been pre-populated via AD.

Thanks for your attention to these issues! I really appreciate the features of this plugin.
–Brandon